In a high-calorie gas appliance (1) which is set with a replaceable fuel gas cassette (9) containing therein liquefied gas and has a burner (7) for burning vaporized fuel gas from the cassette, a heat transfer plate (15) is mounted on the gas appliance with its one end portion disposed near the burner (7) and its the other end portion in contact with the fuel gas cassette (9) so that a part of heat of combustion at the burner (7) is transferred to the fuel gas cassette (9) to heat the same. Further, a heat accumulator member (2) is disposed in contact with the heat transfer plate (15) in the position of contact of the heat transfer plate with the cassette (9). Thus temperature drop of the liquefied gas due to vaporization latent heat in response to gas supply from the cassette is suppressed, thereby ensuring stable gas supply even if the amount of gas in the cassette upon initiation burning is reduced and ensuring exhaustion of the cassette upon quenching.